Z notation

A particular notation for formal specification developed principally at Programming Research Group Oxford University. It is based on set theory, with mechanisms to allow large specifications to be separated into parts and structured. See Spivy (1988).

zero-parameter models

Models that can make a priori predictions of quantitative performance of users on an interactive system. The are called zero-parameters because no parameters need to be set from data collected on the system in question; all numeric parameters can be set through a task analysis and pre-existing data from prior research.

zone of proximal development

The inventory of capabilities people can currently demonstrate with assistance (human and material support) and therefore may, in the future, be able to achieve by themselves.